1. Field of the Invention
The present invention relates to an MEMS gyroscope and, more particularly to the MEMS gyroscope capable of precluding the execution of an off-line calibration process for the error introduced by the sensing circuit defect and by the mechanical structure defect of its gyroscope module. By attaching the MEMS gyroscope to a DUT, the rotating angle of the DUT can be computed without the execution of an integration process.
2. Description of Related Art
In recent years, the application field of the MEMS gyroscope has been enlarged dramatically, such as being used as the angle measuring unit of a motion sensor of a handheld device. However, due to the intrinsic limitation thereof, such as the sensing circuit defect and mechanical structure defect introduced by the MEMS manufacturing process, the precision range of the angle measurement of the MEMS gyroscope still needs to be improved dramatically. As a result, an off-line calibration is required to be executed, after the conventional MEMS gyroscope has been used for measuring angle for a certain amount of times, for limiting the error to be within an acceptable range.
For eliminating the influence of the mechanical structure defect on the precision range of the angle measurement, the industry has promoted several approaches. For example, adopting complex designs on the element of the MEMS gyroscope, executing specially-designed MEMS manufacturing processes, or applying additional post manufacturing processes. However, these approaches will increase the manufacturing cost of the conventional MEMS gyroscope. Moreover, the complex design of the element of the MEMS gyroscope will lower the yield rate of the overall manufacturing process of the conventional MEMS gyroscope. Therefore, further improvement on these approaches is required.
Besides, for eliminating the influence of the sensing circuit defect on the precision range of the angle measurement, the industry has promoted several approaches. For example, modulation, switch capacitor architecture, or correlated double sampling (CDS). These approaches have been applied for eliminating the non-ideal factor (i.e. the sensing circuit defect) commonly seen in the sensing circuit (i.e. the circuit including a variable capacitance capacitor and a charge amplifier), parasitic capacitance produced by the conductive wire, amount of the output signal drift of the operational amplifier, uncertainty of the bias voltage, asymmetry of the differential variable capacitance capacitor. However, these approaches are not only too complex, but also require the additional installation of a related circuit. Thus, these approaches are not favorable to the miniaturizing MEMS gyroscope.
Moreover, in the angle measuring process of the conventional MEMS gyroscope, the angular velocity of the gyroscope module of the MENS gyroscope must be measured first. Then, the rotating angle is obtained after executing an integration process on the measured angular velocity. However, not only the measurement signal is integrated, but also the noise signal, resulting in the error of the measurement of the rotating angle of the conventional MEMS gyroscope always increasing with the duration of the integration process.
Therefore, an MEMS gyroscope capable of precluding the execution of an off-line calibration process for the error introduced by the sensing circuit defect and the mechanical structure defect of its gyroscope module, and of calculating the rotating angle of the DUT without the execution of an integration process is required by the industry.